Electrochemical and Electronic Transport Properties of Perovskite-Type LaMnO₃ Synthesized via an Ultrasound-Assisted Wet-Chemical Method

Perovskite-type LaMnO3 (LMO) was synthesized in a pure-phase form with space group R-3c using a modified wet-chemical “Pechini” process, with assistance from the ultrasound sonication process and microwave calcination. The calcination temperature was found to be 650 °C/3 h, which is at least 100–150 °C lower than the earlier reported calcination temperature for this compound. Rietveld refinement revealed a goodness of fit with χ2 = ∼1.6. The average particle size was 39nm, as demonstrated by scanning electron microscopy (SEM), while the specific surface area was 17.71 m2/g with an average pore size of 27.65 nm. The electrochemical studies in a three-electrode configuration via galvanostatic charge–discharge (GCD) mode revealed a specific capacitance of 63 F/g and a specific capacity of 27.5 mAh/g at a current density of 0.5 A/g. Cyclic voltammetry (CV) studies displayed pseudocapacitive behavior in LMO, thus making LMO a potential candidate for supercapattery applications. Further, the electronic transport properties of LMO were studied via broadband dielectric spectroscopy (BDS) over a wide frequency (0.1–106 Hz) and temperature range (123–523 K). A high dielectric constant (>103), with the hopping of charge carriers being responsible for conduction and thereby dielectric losses in the sample, was revealed by BDS. The conductivity of LMO was found to vary between 10–7 and 10–2 S/cm, with the activation energy of conduction ranging between 0.094 and 0.066 eV above and below room temperatures, respectively.